This invention relates to the stabilization of artificial limbs.
Artificial limbs are generally fitted to patients by a skilled prosthetist utilizing components available in the art to make up the artificial limb. Until recently, artificial limbs were generally of the exoskeletal type, and where the artificial limb was to replace a leg removed above the knee, a complex knee joint was incorporated into the exoskeletal device, usually having some sort of a brake or release mechanism to allow flexing of the knee.
In recent years, the endoskeletal prosthetic device has been developed for use in replacing lower limbs, both in below-the-knee and above-the-knee amputations. An endoskeletal device more closely approximates the human structure in that the strength member usually includes a tubular structure approximating a human bone. By concentrating the strength member into a tubular skeletal-type prosthetic device considerable weight can be saved. Nevertheless, the uniqueness of each prosthetic device still requires individual fitting to the patient. Knee joints and bases to mount a prosthetic foot are currently available for use in such fitting. These devices incorporate adjustment features so that the individual prosthetic device may be fitted to the particular needs of the patient.
Although these adjustable prosthetic devices have proved very useful, they suffer from several drawbacks. First, adjustable fittings loosen after wear and must be reset to the measurements of the patient. Secondly, the adjustable elements may increase the weight of the entire prosthetic device, which is immediately reflected in patient fatigue. Furthermore, the increase in weight of a relatively long prosthetic device necessary in an amputation above the knee imposes a relatively large moment on the patient's relatively short stump. Accordingly, it is appropriate to reduce weight to a minimum in any prosthetic device without loss of strength.
Nevertheless, since each device must be uniquely tailored to the patient, the use of adjustable fittings for the attachment of pylons, the knee joint, and also what suffices to be an ankle joint, has become common. Unfortunately, such adjustable devices, even with their advantages over the old exoskeletal system, still suffer from aforedescribed drawbacks. In particular, the presently marketed adjustable devices will wear and the adjustments will become loose. Therefore, it becomes necessary for the patient to return to the prosthetist to have his prosthesis tightened and readjusted. With the loosening of the prosthesis, noise may be generated in the various joints which, although not critical to the operation of the device, can become embarassing to the user. In extreme cases, the prosthetic foot has been known to loosen to the point of coming off the prosthetic leg at an inopportune moment.
The development of the endoskeletal prosthesis was a great step forward in artificial limbs and the subsequent adjustability feature has been most helpful in obtaining proper fit. However, the adjustability feature is not needed once a satisfactory fit has been obtained. Fixing or stabilizing the rather expensive adjustable fittings is not economically sound, nor particularly sound from an engineering point of view. To weld the expensive adjustable fittings once a satisfactory fit has been obtained would not only be wasteful, but could add unnecessary weight to the prosthesis. Accordingly, a method has been devised and is disclosed herein to overcome the lasting disadvantages of the adjustable prosthesis while temporarily utilizing the adjustable prosthesis to obtain a satisfactory fit on a patient. Along with the method, particular structural elements have been invented to practice the invention.